The present invention relates to new oligomeric organosilicon compounds, a process for their preparation and their use in rubber mixtures and for the production of shaped articles.
It is known to employ sulfur-containing organosilicon compounds, such as 3-mercaptopropyltrimethoxysilane or bis-(3-[triethoxysilyl]-propyl) tetrasulfane, as a silane adhesion promoter or reinforcing additive in rubber mixtures with an oxidic filler content, inter alia for treads and other components of car tires (DE 2 141 159, DE 2 212 239, U.S. Pat. Nos. 3,978,103, 4,048, 206).
It is furthermore known that sulfur-containing silane adhesion promoters are employed in the preparation of sealing compositions, casting moulds for metal casting, paint and protective coating films, adhesives, asphalt mixtures and plastics with an oxidic filler content.
Finally, there are possible uses for these compounds in the fixing of active compounds and functional units on inorganic support materials, e.g. in the immobilization of homogenous catalysts and enzymes, in the preparation of fixed bed catalysts and in liquid chromatography.
It is furthermore known that the formation of rubber mixtures with longer-chain polysulfanes, in particular bis-(3-[triethoxysilyl]-propyl) tetrasulfane, chiefly used for adhesion promotion in such rubber mixtures with an oxidic filler content requires particular care during the processing with the rubber, in order to avoid prevulcanization during mixing of the components. The use of organosilanes with shorter polysulfane chains, in particular with disulfane units, which is advantageous in this respect, has been described in respect of the processing and properties of the vulcanization products in EP-A 0732 362 (corresponding to U.S. Pat. No. 5,580,919) and by Panzer (L. Panzer, Am. Chem. Soc., Rubber Div. Meeting 1997). However, a shortening of the polysulfane chains has the effect of an undesirable, lower crosslinking yield between the oxidic filler and the rubber polymer.
DD 262 231 A1 and EP-B1 0 466 066 describe sulfur-rich, oligomeric organoorganooxysilanes with a cycloalkenyl unit which have the disadvantage, however, that their use as a silane adhesive or reinforcing additive leads to vulcanized products with rather average static and dynamic properties, in particular in tensile strength, breaking energy and tensile stress. Moreover, the preparation of this type of compound is complicated and expensive.
It has now been found that the abovementioned disadvantages of the prior art can be substantially avoided by the use of the new oligomeric organosilicon compounds according to the invention as an adhesion promoter or reinforcing additive in rubber mixtures.